Stop .NET 4 complaining on Windows when it tries to load in DLLs that haven't been marked as trusted in the operating system.

This is done by adding <loadFromRemoteSources enabled="true" /> to the execute *.config files.
This tells .NET 4 to trust the DLLs, which is safe in our case since we are not loading DLLs from locations that untrusted users may specify
Addresses http://opensimulator.org/mantis/view.php?id=6853 and http://opensimulator.org/mantis/view.php?id=6846
As far as I know, CAS policy checks have never been performed in Mono
Fix non-root prim sit positions for prims where a sit target has been specified as well.